Decorative preparations for producing gold-containing decorations from substrates which can be fired such as glass, porcelain and other ceramic substances, are known. These are, inter alia, so-called bright gold and burnished gold preparations which can be used to produce high-gloss or silk matt gold film decorations. Preparations with similar compositions and lower gold contents, and frequently also a concentration of dissolved compounds of other metals, such as in particular those of Ti, V, Cr, Fe, Co, Ni, Sn, Bi and Zr, are used as luster preparations which have an iridescent lustrous glaze with a color which depends on the metal composition. Finally, purple decorative colors and the preparations containing these are also known, these containing colloidal gold in and/or on an inorganic matrix, in particular glass fluxes, as the color-providing component.
Bright gold, burnished gold and luster preparations contain a gold compound in dissolved form, in a liquid support medium whose main components are an organic binder and a solvent. These gold compounds are generally gold(I) thiolates and gold sulphoresinates. Whereas gold thiolates and gold sulphoresinates, which are only soluble in organic solvents, were previously available for the purpose mentioned above, now water-soluble gold(I) thiolates are also known; reference is made here, for example, to EP-A 0 514 073 and EP-A 0 688 265 in which these types of thiolates in bright gold and burnished gold preparations and their composition are specifically disclosed. Burnished gold preparations often also contain gold powder and/or an insoluble gold compound. The decorative preparations mentioned also generally contain fluxes and auxiliary agents to adjust the processing and wear properties. The fluxes are in particular soluble compounds of the elements B, Si, V, Cr, In, Zn, Sb, Bi and Rh, wherein in particular Rh has a beneficial effect on the gloss and Cr and Bi have a beneficial effect on adherence of the gold film to the substrate. Although a person skilled in the art already has a wide range of gold(I) thiolates available, there is also interest in new sources of gold for use in the preparations mentioned above.
Decorative preparations with a purple pigment based on colloidal gold have been known for a long time. The methods of manufacture are sometimes very expensive and/or do not lead to sufficiently thermally stable pigments which results in discoloration of the colors at high firing temperatures, in particular above 1000.degree. C. For example, reference is made here to DE-A 44 11 103, also to German patent application 196 49 067.7 which has not yet been published.